Method for false-twisting a synthetic filament yarn

ABSTRACT

In the method, the yarn is heated at a temperature at which the yarn is plasticized. The yarn is then passed through a closed path formed around a pin while contacting the periphery of the pin. A portion of the yarn emerging from the closed path is brought into contact with a portion of the yarn entering the closed path. The entering and the emerging portions of the yarn are entwined with each other at entry and exit regions of the closed path in such a manner that each portion of the yarn goes around the other in at least one turn under friction while travelling in the same direction.

United States Patent [191 Inuyama et al.

[451 Feb. 12, 1974 METHOD FOR FALSE-TWISTING A SYNTHETIC FILAMENT YARN[75] Inventors: IIisao Inuyama, Otsu; Sadao Tomioka, Kusatsu; YoshihikoChiba, Kyoto, all of Japan [30] Foreign Application Priority Data3,035,396 5/1962 Biggers 57/157 MS 3,148,520 9/1964 Biggers..... 57/157MS 3,178,795 4/1965 Warthen 57/157 MS FOREIGN PATENTS OR APPLICATIONS227,591 4/1960 Australia 57/157 TS Primary Examiner-John PetrakesAttorney, Agent, or FirmAllan Ratner ABSTRACT In the method, the yarn isheated at a temperature at which the yarn is pla'sticized. The yarn isthen passed through a closed path formed around a pin while contactingthe periphery of the pin. A portion of the yarn emerging from the closedpath is brought into contact with a portion of the yarn entering theclosed path. The entering and the emerging portions of the yarn areentwined with each other at entry and exit regions of the closed path insuch a manner that each portion of the yarn goes around the other in atleast one turn under friction while travelling in the same direction.

7 Claims, 14 Drawing Figures PATENTEB FEB 1 2 I974 SHE! 3 0F 5PATENTEHFEB 12 m4 SHEEI II [If 5 6'0 9'0 ""CROSS ANGLE (sf) (DEGREE)ZOOO- F/QS METHOD FOR FALSE-TWISTING A SYNTHETIC FILAMENT YARN Thepresent invention relates to a method and apparatus for false-twisting asynthetic filament yarn, more particularly, relates to a method andapparatus for false-twisting a thermoplastic synthetic monoormultifilament yarn so as to result in a textured yarn having a hightorque and little or no crimp.

In the conventional method, the synthetic filament yarn is false-twistedby using a spindle and there is an upper limit to the rotation number ofthe spindle, hence, there is an upper limit to the velocity ofprocessing of the false-twisting. Particularly, there is thedisadvantages that the productivity of the textured yarn from finedenier filament yarn is relatively low.

The conventional friction drive method for falsetwisting the filamentyarn can be carried out with a high productivity at a large twistnumber. However, this method has the disadvantages that the frictionmember used for false-twisting the filament yarn must be made of aspecial hard material having a high resistance against rubbing and thatit is very difficult to control the twist number for the filament yarnbecause the frictional property of the frictional member varies owing totransfer of the oiling agent applied to the filament yarn to thefriction surface thereof.

Further, the textured yarns produced by the abovementioned conventionalfalse-twisting method have a high bulkiness due to the highly crimpedfilaments, but the torque is relatively low.

There is also a prior art wherein a filament yarn passing across a wireor filament yarn which is itself travelling longitudinally, makescontact with the wire or filament yarn at one point under friction. Thefilament yarn is false-twisted by the forward travel of the wire orfilament yarn, and the resultant textured yarn has a high bulkiness dueto the crimp of the filaments. However, it is known that the abovemethod cannot produce textured yarn having a high torque.

As stated above, the conventional false-twisting method can produce atextured filament yarn having a high crimp and bulkiness but can notprovide a textured yarn having a high torque and little or no crimp.Such textured yarn having a high torque and little or no crimpissuitable for knitted articles, especially, hosiery, and more especially,stockings. The knitted articles high stretchability, a beautifulappearance and an elegant hand feeling. For the above-stated advantages,the high torque textured filament yarns have been recently spot-lightedand demand for them increases.

An object of the present invention is to provide a method and apparatusfor false-twisting a synthetic filament yarn into a textured yarn havinga high torque and which are substantially no crimp.

Another object of the present invention is to provide a method andapparatus for false-twisting a synthetic filament yarn at a highprocessing velocity into a textured yarn having a high torque.

A further object of the present invention is to provide produced fromthe high torque textured yarn have a a method and apparatus forfalse-twisting a synthetic vention. The method of the' present inventionincludes the step of heating a synthetic monoor multi-filament yarn at atemperature at which the yarn is plasticized by passing the yarn throughthe heating means, and the step of false-twisting the yarn by passingthe yarn through a closed path formed around a pin, the yarn enters intoand emerges from the closed path while contacting the periphery of thepin, and, at entry and exit regions of the closed path, a portion of theyarn entering into the closed path and a portion of the yarn emergingfrom the closed path are entwined with each other in at least one turnunder friction while travelling in the same direction, whereby theentering portion of the yarn is twisted by the forward travel of theemerging portion and a portion of the yarn emerged from the closed pathis untwisted by the forward travel of the entering portion.

In the above method, since the yarn is entered into and emerged from theclosed path while keeping contact with the periphery of the pin, thetwine portion is secured between points of contact at which the portionsof the yarn entered into and emerging from the closed path are incontact with the periphery of the pin. This is an advantageous featureof the method of the present invention because this results in a uniformprocessing of the false-twisting.

The apparatus of the present invention comprises a feed means for amonoor multi-filament yarn, heating means for the yarn disposeddownstream of the feed means, means for defining a closed path for theyarn disposed downstream of the heating means and containing at leastone pin on the periphery ofwhich a portion of the yarn entering into theclosed path and a por tion of the yarn emerging from the closed path areentwined with each other in at least one turn, and delivery means forthe yarn disposed downstream of the closed path-defining means.

ln order to produce the textured filament yarn having a high torque andlittle or no crimp, it is necessary to satisfy the following condition:

1. The filament yarn is uniformly false-twisted under a predeterminedcondition.

2. The false-twisted filament yarn is sufficiently heatset at thetwisted form and thereafter, untwisted.

3. in the false-twisting process, the filament yarn is deformed at ahigh torsion and low flexure.

in the case where two filament yarns travelling through paths differentfrom each other and intersecting each other, are false-twisted each bythe forward travel of the other filament, the twist number of theresultant false-twisted yarn depends on the travelling velocity of theyarns, intersecting angle between the yarns, filament number in theyarns, and diameter and frictional efficiency of the yarn.

The above-mentioned relationship is summarized in the following equation(l):

T B' VSinO/rrdl/V B" Sin0/1rd(l a) wherein T represents the twist numberin turns/m, V the velocity in m/min of yarn emerging from the entwiningregion, V the velocity in m/min of the yarn entering into the entwiningregion, a the diameter in mm of the yarn, B the frictional coefficiencyof the yarn, 0 the twine angle between the entering portion and theemerging portion of the yarn, and a the shrinkage of the yarn due totwist of the yarn which is equal to V V V.

The twine angle 6 of the yarn used herein means an angle between theaxis lines of each of the yarns entwined with each other, The frictionalcoefficient [3 is a variable which varies with the frictionalcoefficient, contact area and contact pressure of the yarns entwinedwith each other. That is, the diameter, filament number and frictionalcoefficient of the yarns depend on the kind of the filament yarns used,hence, in the case where preselected filament yarns are false-twisted ata predetermined velocity, the twist number can be adjusted bycontrolling the twine angle and contact area and pressure between theyarns twined with each other. The contact pressure of the yarns can beadjusted by controlling the tension on the filament yarns.

Also, the twine angle is adjusted by controlling the cross angle betweenthe portion of the yarn just entered into the closed path and theportion of the yarn just emerged from the closed path. Accordingly, thetwist number can be adjusted by controlling the cross angle as definedabove and the tension of the yarns. The method of controlling the crossangle will be illustrated in detail hereinafter.

In the method of the present invention, the filament yarn to befalse-twisted is heated at a temperature at which the yarn isplasticized and then passed through a closed path, and at entry and exitregion of the closed path, the entering portion and the emerging portionof the yarn are entwined with each other in at least one turn underfriction. Such heating and entwining results in the followingadvantages.

1. In the conventional method as stated above, the entering and emergingportions of the yarn intersect each other so as to make contactsubstantially at one point. Compared with this, in the method of thepresent invention, the entering and emerging portions of the yarn areentwined with each other so as to make contact over a certain length.Therefore, it is obvious that the frictional efficiency [3 in the methodof the present invention is higher than that of the conventional method.Such high frictional efficiency derived from the method of the presentinvention results in a twist number greater than that of theconventional method.

2. The entering and emerging portions of the yarn are pressed to eachother at the region in which they are twined with each other so as toenhance the frictional efficiency [3, and hence, to increase the twistnumber.

3. The pressure on the portions of the yarn in the twine region of theclosed path causes a decrease of bending of the yarn in the twistingprocess. Therefore, in the false-twisting process according to thepresent invention, the filament yarn is highly twisted and slightlybent, and the filaments in the yarn slightly migrate owing to thepressure. Such slight bending of the yarn and migration of the filamentsin the false-twisting process is very effective for preventing the yarnfrom crimping. Also, the high twist of the yarn results in an enhancedtorque of the yarn.

4. According to the method of the present invention, the portion of yarntravelling toward the closed path is heated by the heater locatedupstream of the closed path at a temperature at which the yarn isplasticized and then cooled between the heater and the closed path whilebeing twisted by the forward travel of the portion of the yarn emergingfrom the closed path. Accordingly, the portion of the yarn travellingtoward the closed path is heat-set in the twisted form at a regionupstream of the closed path. Next, the twisted and heat-set portion ofthe yarn enters into the closed path and is untwisted in the entryregion of the closed path by the forward travel of the emerging portionof the yarn. However, this untwist is very slight since the enteredportion of the yarn makes contact briefly with the periphery of the pin,and advances along the periphery of the pin in the twisted form. Whenthe twisted portion of the yarn reaches the exit region of the closedpath, the twisted portion is further-twisted very slightly by theforward travel of the entering portion of the yarn. Then, when thetwisted yarn emerges from the closed path, the emerging portion of theyarn is completely untwisted by the forward travel of the enteringportion of the yarn. Accordingly, the yarn passes through the closedpath in the twisted form under tension. This passing of the twisted yarnunder tension is effective for enhancing the torque of the yarn and forlowering the crimp of the yarn.

In the conventional false-twisting process, in order to produce texturedyarn having a high crimp and a high bulkiness, the filament in the yarnis certainly migrated and bent outwardly so as to increase the diameterof the yarn. Compared with this, in the false-twisting according to thepresent invention, the filament in the yarn is prevented from migrationand bending so as not to increase the diameter of the yarn. This resultsin the high torque and low crimp of the textured yarn obtained from themethod of the present invention.

Textured yarn having an optimum torque can be prepared by false-twistingat an optimum twist number which depends on the total denier of the yarnand number of filaments in the yarn. That is, if the twist number isexcessively large the resultant textured yarn has undesired crimp, andif the twist number is excessively low, the resultant textured yarn hasa non-uniform torque. For example, six kinds of nylon 66 filament yarnshaving filament counts of 17 denier/3 filaments, 20 denier/2 filaments,2O denier/3 filaments, 22 denier/3 filaments, 25 denier/3 filaments and25 denier/5 filaments, were false-twisted by the method of the presentinvention at various twist numbers, and crimping property of theresultant textured yarns and evenness of knitted fabric from theresultant textured yarns were observed.

The results of the observations are shown in Table l Filament count Item17 DH F 20 D/2 F 20 D/3 F 22 0/3 F 25 D/3 F 25 D/S F Twist number at2300 2500 2100 2000 I900 1600 which crimp is created Twist number at2000 2300 1900 I800 I700 1300 which uneven fabric results Optimum twist2170 2450 2000 I910 I790 I390 number The optimum twist nu nibersmentioned above were obtained emprically for the above experimentation.The twist number at which uneven fabric results varies depending on thestructure of the fabric and tension during fabric-producing process.Therefore, the twist numbers at which uneven fabric results as shown inTable 1 are not always the lower limit of the twist number for thevariously yarns in the method of the present invention. Sometimes, atwist number which is lower than the twist number at which uneven fabricresults as shown in Table 1, results in a uniform fabric.

From the above-stated experiment, in order to obtain a texturedmulti-filament yarn having an optimum torque, it is preferable that themulti-filament yarn is twisted at a twist number satisfying thefollowing relationship (II):

1 wherein T represents the twist number in turn/meter, D

the denier of the yarn and f the numbers of filaments in the yarn and fa 2.

The optimum twist number for the filament yarn is selected inconsideration of the use of the resultant textured yarn. If it isdesired that the textured yarn has a very high torque, the filament yarnis false-twisted at the upper limit of the twist number satisfying therelationahip (11). However, if it is desired that the textured yarn hasa relatively low torque, the filament yarn is false-twisted at arelatively low twist number satisfying the relationship (11).

In consideration of processing efficiency, tension and temperature whichvary during the false-twisting process, it is more preferable that theyarn is twisted at the twist number satisfying the followingrelationship (Ill).

15480/ V D'fX 0.40 T 15480/ VDfX 0.95

In the case where the yarn is composed of a monofilament, even when thetwist number is larger than 15480] V Of, the resultant textured yarn hasno crimp.

The present invention provides a method and device for adjusting thecross angle between a portion of the yarn just entered into the closedpath and a portion of the yarn just emerged from the closed pass inorder to control the twist number of the yarn.

The method and apparatus of the present invention will be explained indetail by the following illustration and the accompanying drawings inwhich;

FIG. 1 is aschematic view of an embodiment of the apparatus of thepresent invention,

FIGS. 2A and 2B are schematic views showing the relationship between thedirection of entwining of yarns and the direction of twisting of theyarns,

FIG. 3 is a schematic view ofanother embodiment of the apparatus of thepresent invention,

FIGS. 4A, 4B and 4C are all schematic views showing the relationshipbetween the position of a rotatable roller in the closed path the crossangle d) between a por- 6 tion of yarn just entered into the closed pathand a portion of yarn just emerged from the closed path in the apparatusof FIG. 3,

FIGS. 5A and 5B are both schematic views showing the relationshipbetween the diameter of the fixed pin and the cross angle :12 in theapparatus of FIG. 1,

FIG. 6 is a schematic view showing the relationship between the positionof the fixed pin and the cross angle (1:,

FIG. 7 is a graph showing the relationship between the cross angle (1)and twist number,

FIG. 8 is a graph showing the relationship between the diameter of thefixed pin and twist number,

FIG. 9 is a graph showing the relationship between the denier of thefilament yarn and twist number,

FIG. 10 is a schematic view showing a conventional false-twisting methodother than the method of the present invention.

Referring to FIG. 1, a filament yarn 2 is fed by means of a pair of feedrollers 4 from a feed package 1 onto the heater 5 through a guide 3. Theyarn 2 is heated by the heater 5 to a temperature at which the yarn 2 isplasticized, cooled downstream of the heater 5 and then wound on theperiphery of a fixed pin 6 in at least one turn so as to form a closedpath 12 around the fixed pin 6. At an entry and exit region 7 of theclosed path 12, a portion of the yarn 2 entering into the clpsed pathand a portion of the yarn 2 emerging from the closed path are entwinedwith each other in at least one turn. The portion of the yarn 2 emergedfrom the closed path 12 is delivered by a pair of delivery rollers 8 andthen wound up by means ofa driving roller 10 into a take-up package 11through a guide 9.

Referring to FIGS. 2A and 2B, the yarn 2 travels through a closed path12 formed around the periphery of the fixed pin 6. At the entry and exitregion 7, a portion 13 of the yarn 2 entering into the closed path 12and a portion 14 of the yarn 2 emerging from the closed path 12 areentwined with each other. In FIG. 2A, the portion 13 of the yarn 2 isentwined about the portion 14 of the yarn 2 in the S direction, andtwisted in the S direction by the forward travel of the portion 14. Asshown in FIG. 1, since the heater 5 is disposed upstream of the closedpath 12, the yarn twisted in the S direction is heat-set by the heater5, and cooled between the heater 5 and the pin 6. When the twisted andheat-set portion of the yarn 2 advances into the closed path 12, theportion 16 of the yarn 2 is slightly untwisted in the Z direction by theforward travel of the emerging portion 14 because the entered portion 16of the yarn 2 immediately contacts the periphery of the fixed pin 6 soas to prevent untwisting of the portion 16. In other words, owing to thecontact of the portion 16 with the periphery of the fixed pin 6, the Stwists of the yarn 2 are retained during the advance along the peripheryof the fixed pin 6. When the S twisted portion of the yarn 2 approachesthe exit region of the closed path 12, the emerging portion 14 of theyarn 2 is slightly further twisted in S direction by the forward travelof the entering portion 13 of the yarn 2 because the emerging portion 14contacts the periphery of the fixed pin 6. Thereafter, the yarn 2 passesthrough the region 7 of the closed path 12 wherein the entering andemerging portions 13 and 14 of the yarn are entwined with each other inat least one turn. The portion 17 of the yarn 2 emerged from the closedpath 12 is entirely untwisted in the Z direction by the forward travelof the entering portion 13 of the yarn 2.

As stated above, the twisting of the emerging portion 13 and theuntwisting of the entered portion 14 are very slightly carried out inthe closed path 12, and thus, they are negligible.

Accordingly, in the false-twisting according to the method as shown inFIG. 2A, substantially, the portion 13 of the yarn 2 entering into theclosed path 12 is twisted in the S direction and the portion 17 of theyarn 2 emerged from the closed path is entirely untwisted in the Zdirection. The resultant textured yarn has a high torque in the Zdirection.

In FIG. 2B, the entering portion 13 and the emerging portion 14 of theyarn 2 are entwined in the Z direction. Accordingly, the enteringportion 13 is twisted in the Z direction by the forward travel of theemerging portion 14 and heat-set by the heater as shown in FIG. 1, andthe emerged portion 17 is untwisted in the S direction by the forwardtravel of the entering portion 13. The resultant textured yarn from themethod as shown in FIG. 28 has a high torque in the S direction. Thatis, according to the method of the present invention, the twistdirection of the yarn can be easily established by selecting theentwining direction of the entering and emerging portions of the yarn 2.

As shown in FIGS. 2A and 2B, the entering portion 13 and the emergingportion of the yarn 2 are entwined with each other while in contactaround the periphery of the fixed pin 6. The entwined portions of theyarn 2 are kept on or near the periphery of the fixed pin 6.

In order to keep the entwined portions of the yarn on or near theperiphery and to avoid creation of excessive friction between the fixedpin periphery and the yarn, it is necessary that the diameter of thefixed pin is not too large. That is, generally, it is preferable thatthe diameter of the fixed pin is in a range from 0.8 to 3.0 mm. Also, itis necessary that the fixed pin periphery has a low frictionalcoefficient and a high resistance to rubbing. Accordingly, in general,the fixed pin is made of ruby, sapphire or alumina ceramic.

In the method and apparatus of the present invention, it is preferablethat the pin for defining the closed path is fixed in a non-rotatablecondition, but, sometimes, it is allowable for the pin to be rotatable.

Referring to FIG. 3, the closed path 12 is defined by the fixed pin 6and a rotatable guide roller 15.

As stated hereinbefore, the twist number varies with variation of thecross angle between the emerged portion 17 and the entered portion 16 ofthe yarn 2, and when the cross angle is 90, the entering portion 13 istwisted at a maximum twist number.

In FIGS. 4A, 4B and 4C, the cross angle (1: can be varied by moving therotatable guide roller along the direction of the arrows indicated inthe drawings. That is, comparing FIG. 48 with FIG. 4A, when the guideroller 15 is approached to the emerged portion 17, the cross angle 4) isdecreased so as to decrease the twist number.

As shown in FIG. 4C, when the guide roller 15 is approached to the fixedpin 6, the cross angle d: is decreased. Also, comparing FIG. 4A withFIG. 4C, an increase of the diameter of the guide roller 15 results indecrease of the cross angle (1).

Referring to FIGS. 5A and 5B, the fixed pin 60 shown in FIG. SA has adiameter smaller than that of the fixed pin 61) shown in FIG. 5B. Thisresults in the fact that the cross angle (pa in FIG. 5A is larger thanthe cross angle (15b in FIG. 58. That is, the cross angle d) can also bevaried by changing the diameter of the fixed pin.

Referring to FIG. 6, the cross angle (1) is varied by moving the fixedpin 6 along the direction of the arrow as shown in the drawing.

In FIG. 7, a curve (a) shows the relationship between the twist numberand the cross angle 4) when a nylon 66 filament yarn of 20 denier/3filaments was falsetwisted by entwining in one turn, utilizing theapparatus as shown in FIG. 3 wherein a rotatable guide roller of 15 mmdiameter is arranged at a distance of 25 mm from a fixed sapphire pin of2 mm diameter, at a feed rate of 700 m/min, under a tension of 0.3 g/d.The curve (b) shows the same relationship as that of the curve (a)except that the yarn is entwined in two turns. From the curves (a) and(b), it is clear that the closer the cross angle approaches the more thetwist number increases.

FIG. 8 shows the relationship between the diameter of the fixed pin andthe twist number when a nylon 6 filament yarn of 20 denier/3 filamentsis false-twisted at a feed rate of 700 m/min under a tension of 0.3 g/dby utilizing the apparatus as shown in FIG. 1 using several fixedsapphire pins having diameters different from each other. As is clearlyshown in FIG. 8, the greater the diameter of the fixed pin, the less thetwist number.

FIG. 9 shows the relationship between the twist number, denier of yarnand number of filaments in the yarn when nylon 6 filament yarns ofdenier and numbers of filaments different from each other arefalse-twisted by means of an apparatus as shown in FIG. 3 using a fixedsapphire pin of 2 mm diameter, and a feed rate of 700 m/min under atension of 0.2 g/d. From the drawing, it is clear that the greater thedenier of the yarn and the greater the number of filaments in the yarn,the less the twist number of the textured yarn false-twisted accordingto the method and apparatus of the present invention.

When the textured yarn manufactured by the method and apparatus of thepresent invention is freely suspended, it rotates in a directionopposite to that of the false-twisting until it reaches a stationarycondition or creates snarls, but substantially does not create crimp.Accordingly, the fabric from the textured yarn according to the presentinvention has a low bulkiness, high stretchability,- smooth appearanceand elegant hand feeling.

The method and apparatus of the present invention does not require arotor member rotating at a high velocity such as a spindle andfrictional member. Hence, the apparatus of the present invention is verysimple in its construction and can falst-twist the yarn at a very highvelocity, for example, 500 to 2,000 m/min. It is accordingly possible toconnect the false-twisting step of the present invention to the spinningand drawing step of the filament yarn so as to continuously carry outspinning, drawing and false-twisting steps. Also, the method andapparatus of the present invention can be carried out at a very lowprocessing cost.

The examples which follow are given for the purpose of illustrating indetail the present invention.

Example 1 A nylon 66 filament yarn of 25 denier/3 filaments wasfalse-twisted in the S direction and the Z direction by utilizing anapparatus as shown in FIGS. 1, 2A and 28 using a fixed sapphire pin of0.8 mm diameter under the following conditions:

Tension on the yarn upstream to the pin: 5 g Tension on the yarndownstream from the pin: 24 g Feeding rate of the yarn: 300 m/min Heatertemperature: 180C Heating time: 0.5 second Cross angle (it): 80 Twinenumber: I turn The yarn was false-twisted at a twist number of 2,300turns/meter and converted to a textured yarn having a tenacity of 98 g,an elongation at break of 12 percent and a snarl index of 32.

The snarl index above represents the magnitude of the torque of thetextured yarn and is determined in the following manner. A yarn isstressed between a fixed end support and a movable end support such thatthe length under a tension of 0.1 g/denier is 50 cm.

A weight of 50 mg is hung at the center of the yarn. The movable endsupport is moved toward the fixed end support. When the yarn is firstsnarls at atravel length of in X cm, the snarl index is determined fromthe equation:

Snarl Index (50 X) X 2 The resultant textured yarn had no crimp.

A stocking was knitted from the resultant textured yarns of S and Ztorques by alternately feeding them. The resultant stocking had a highstretching property and a soft touch.

For comparison, the above false-twisting procedure was repeated exceptthat the yarn was merely intersected at a point as shown in FIG. insteadof entwining the yarn.

The resultant textured yarn had numerous crimps and no torque.

Example 2 Apolyetlyleneterephthalate filament yarn of 50 de- [tier/l2filaments was false-twisted in the S and Z directions by means ofapparatus the same as that used in Example 1 under the followingconditions:

Tension on the yarn upstream to the pin: 6 g Tension on the yarndownstream from the pin: 30 g Feeding rate of the yarn: 250 m/min Heatertemperature: 220C Heating time: 0.6 second Cross angle (4)): 85 Twinenumber: I turn Example 3 A nylon 6 mono-filament yarn of denier wasfalse twisted in the S and Z directions by means of the apparatus thesame as that used in Example 1 under the following conditions.

Tension on the yarn upstream of the pin: 4 g Tension on the yarndownstream from the pin: 20 g Feeding rate of the yarn: 500 m/min Heatertemperature: 180C Heating time: 0.3 second Cross angle 5): 85 Twinenumber: 2 turns The mono-filament yarn was false-twisted at a twistnumber of 1,800 turns/meter and converted to a torque yarn having atenacity of g, an elongation at break of 15 percent and a snarl index of56. The resultant torque yarn had no crimp.

A stocking was prepared from the resultant S and Z torque yarns byalternately feeding them. The resultant stocking had a high stretchingproperty and a uniform appearance.

Example 4 A nylon 6 mono-filament yarn of 20 denier having an originaltwist of 14 turns/meter in the S direction was false-twisted in the Sdirection by the apparatus as shown in FIG. 6 containing a rotatable pinof 15 mm diameter under the following conditions.

Tension on the yarn upstream of the pin: 4 g Tension on the yarndownstream from the pin: 25 g Feeding rate of the yarn: 500 m/min Heatertemperature: l80C Heating time: 0.3 second Cross angle (4)): 60

Twine number: I turn The false-twisting was effected at a twist numberof 2,100 turns/meter, and the yarn was converted to a torque yarn havinga snarl index of 54.5 and no crimp.

For comparison, the above procedure was repeated except that the yarnwas merely intersected in the manner shown in FIG. 10 instead of twiningthe yarn. The false-twisting was carried out at a twist number of 762turns/meter and the yarn was converted to a crimped yarn having numerouscrimps and no torque.

Example 5 Example 6 A nylon 6 filament yarn of 20 deniers/3 filamentswas false-twisted in the S and Z directions by employing the apparatusshown in FIGS. 3, 4A and 48 comprising a fixed sapphire pin of 2 mmdiameter and a rotatable guide roller of 15 mm diameter disposed at adistance of 2.5 cm from the pin center to the roller center under thefollowing condition:

'I'cnniun on the yarn upstream of the pin: 4 g 'l'ension on the yarndownstream from the pin: l4 g Feeding rate of the yarn: 700 m/minTemperature of heater: Distributed in 2l0-l9U-l80C Time of heating: 0.]second Cross angle ()I 50 Twine number: 1 turn The yarn wasfalse-twisted at a twist number of 1,500

turns/meter and converted to a torque yarn having a tenacity of 82 g, asnarl index of 43 and no crimp.

The resultant S and Z torque yarns were used for the manufacture of astocking by alternately feeding them. The resultant stocking had a highstretching property and uniformity and elegant hand feeling.

For comparison, the above procedure was repeated except that the yarnwas merely intersected on the periphery of the fixed pin instead ofentwining the yarn. The yarn was converted to a textured yarn havingnumerous crimps and no torque.

What we claim is:

l. A method of producing a high torque filament yarn comprising thesteps of heating a thermoplastic synthetic mono or multifilament yarn ata temperature at which said yarn is plasticized;

passing said yarn through a closed path formed around a pin whilecontacting the periphery of said pin, and;

bringing a portion of said yarn emerging from said closed path intocontact with a portion of said yarn entering into said closed path,

said entering and emerging portions of said yarn being entwined witheach other at entry and exit regions of said closed path in such amanner that each portion of said yarn goes around the other in at leastone turn under friction while travelling in the same direction.

2. A method as claimed in claim 1, wherein said closed path is formedaround a fixed pin.

3. A method as claimed in claim 1, wherein said closed path is formedaround a rotatable pin.

4. A method as claimed in claim 1, wherein said closed path is formedaround a fixed pin and a rotatable guide roller disposed apart from saidfixed pin.

5. A method as claimed in claim 1, wherein the number of false-twists inturn/meter of said yarn is less than 15480/ W wherein D is the denier ofsaid yarn and f is the number of filaments in said yarn.

6. A method as claimed in claim 5, wherein said falsetwist number is ina range from 15480/ l. f X 0.40 to 15480/ VWX 0.95 in turn/meter.

7. A method as claimed in claim 1, wherein the falsetwist number iscontrolled by adjusting the cross angle between a portion of said yarnjust entered into the closed path and a portion of said yarn justemerged from the closed path.

1. A method of producing a high torque filament yarn comprising thesteps of heating a thermoplastic synthetic mono- or multifilament yarnat a temperature at which said yarn is plasticized; passing said yarnthrough a closed path formed around a pin while contacting the peripheryof said pin, and; bringing a portion of said yarn emerging from saidclosed path into contact with a portion of said yarn entering into saidclosed path, said entering and emerging portions of said yarn beingentwined with each other at entry and exit regions of said closed pathin such a manner that each portion of said yarn goes around the other inat least one turn under friction while travelling in the same direction.2. A method as claimed in claim 1, wherein said closed path is formedaround a fixed pin.
 3. A method as claimed in claim 1, wherein saidclosed path is formed around a rotatable pin.
 4. A method as claimed inclaim 1, wherein said closed path is formed around a fixed pin and arotatable guide roller disposed apart from said fixed pin.
 5. A methodas claimed in claim 1, wherein the number of false-twists in turn/meterof said yarn is less than 15480/ Square Root D.f wherein D is the denierof said yarn and f is the number of filaments in said yarn.
 6. A methodas claimed in claim 5, wherein said false-twist number is in a rangefrom 15480/ Square Root D.f X 0.40 to 15480/ Square Root D.f X 0.95 inturn/meter.
 7. A method as claimed in claim 1, wherein the false-twistnumber is controlled by adjusting the cross angle between a portion ofsaid yarn just entered into the closed path and a portion of said yarnjust emerged from the closed path.